MOSASAURUS. — 37 
semblance, both in form and size, with one of the specimens figured by Dr. Gibbes 
as characteristic of his Amphorosteus Brumbyi.' 
2. The bodies of two large cervicals or anterior dorsals. ‘The specimens, together 
with small fragments of a huge skull, were found in the first bed of Green-sand 
at Holmdale, Monmouth County, N. J. They are too much mutilated for detailed 
description, but are interesting on account of their size, as they measure a trifle over 
four inches in length. From their under part projects a robust, cylindroid hypapo- 
physis, which, in both specimens, is broken at the extremity. 
3. A specimen consisting of a paix of large posterior dorsals or lumbars, and part 
of a third with the bodies coossified by means of an irregular exostosis surrounding 
the articular surfaces. It belongs to Rutger’s College, and though its locality is 
unknown, it is supposed by Prof. Cook to have been derived from the deepest layer 
of the Green-sand of Monmouth County, N. J. The anterior pair of vertebral 
bodies together measure seven inches in length; the anterior concave surface of the 
first body is about four inches in diameter, and the vertebral canal, retained entire, 
is transversely elliptical, and measures eleven lines wide and eight lines high. 
From Nebraska Territory, the museum of the Academy of Natural Sciences has 
received a collection of remains of Mosasaurus, consisting chiefly of vertebre, 
which were discovered by Dr. F. V. Hayden. The specimens are as follows :— 
1. Several fragments of weather-worn rock, originally from the same mass, con- 
taining a series of sixteen caudal vertebrae, two others of small size detached from 
the series, and several bones of the extremities. The specimens were obtained on 
the Yellowstone River, and the bones all appear to have belonged to the same 
individual. The rock in which the fossils are imbedded bears some resemblance to 
that described by Dr. Goldfuss, as containing the Mosasaurus skeleton from the 
vicinity of the Big Bend of the Missouri River. It is a very hard, brittle, argilla- 
ceous limestone, amorphous, and of a dark, dull leaden hue. On the surface it has 
become softened, by the action of the weather, into a yellowish-gray material. The 
rock adheres so tenaciously to the equally brittle bones that they have been seriously 
injured in the attempt to expose them. The vertebra, several of which are repre- 
sented in Figs. 15, 16, Plate VII, present the anatomical characters ascribed to the 
posterior caudals of Mosasaurus by Cuvier, Goldfuss, and others. All had coossified 
chevron bones; and the anterior of the series have rudimental transverse processes, 
which entirely disappear in the more posterior ones. ‘The body of the first of the 
series measures nineteen lines in length and twenty-three lines in height and width; 
that of the last is fourteen lines in length and twenty lines in height and width. 
The better preserved of the detached caudals, represented in Fig. 16, Plate VII, 
has its body only nine lines in length. 
2. Two bodies of posterior caudals, well preserved, from Cheyenne River. They 
had coossified chevron bones and no trace of transverse processes. ‘They measure 
fourteen lines in length, eighteen high, and nineteen wide. One of the specimens 
is represented in Figs. 17, 18, Plate VII. 
3. Two caudal bodies, of the same form as the preceding, but rather larger, from 
4 Mem. on Mosasaurus, Plate III, Figs. 14, 15, 16. 
